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Merged
gkjohnson merged 3 commits into from
Apr 10, 2026
Merged

feat: parse <inertial> elements and joint effort/velocity limits #330

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518c8b0
Added missing joint limit and link inertial data
dkozma Nov 13, 2024
622a2d8
Add tests
dkozma Nov 21, 2024
ae7014a
refactor: address PR review feedback from maintainer
ferrolho Apr 9, 2026
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12 changes: 10 additions & 2 deletions javascript/README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -266,10 +266,10 @@ The type of joint. Can only be the URDF types of joints.
### .limit

```js
.limit : { lower : number, upper : number }
.limit : { lower : number, upper : number, effort : number, velocity : number }
```

An object containing the `lower` and `upper` constraints for the joint.
An object containing the `lower` and `upper` position constraints, as well as the `effort` and `velocity` limits for the joint. All fields default to zero if not specified in the URDF.

### .axis

Expand Down Expand Up @@ -357,6 +357,14 @@ name : string

The name of the link.

### .inertial

```js
inertial : { mass : number, origin : { xyz : number[], rpy : number[] }, inertia : { ixx, ixy, ixz, iyy, iyz, izz : number } }
```

The inertial properties of the link parsed from the `<inertial>` element. All fields default to zero if not specified in the URDF.

## URDFRobot

_extends [URDFLink](#URDFLink)_
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14 changes: 13 additions & 1 deletion javascript/src/URDFClasses.d.ts
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Expand Up @@ -19,9 +19,21 @@ export class URDFVisual extends URDFBase {

}

export interface URDFInertial {

mass: number;
origin: { xyz: number[], rpy: number[] };
inertia: {
ixx: number; ixy: number; ixz: number;
iyy: number; iyz: number; izz: number;
};

}

export class URDFLink extends URDFBase {

isURDFLink: true;
inertial: URDFInertial;

}

Expand All @@ -34,7 +46,7 @@ export class URDFJoint extends URDFBase {
jointType: 'fixed' | 'continuous' | 'revolute' | 'planar' | 'prismatic' | 'floating';
angle: number;
jointValue: number[];
limit: { lower: number, upper: number }; // TODO: add more
limit: { lower: number, upper: number, effort: number, velocity: number };
ignoreLimits: boolean;
mimicJoints: URDFMimicJoint[];

Expand Down
27 changes: 26 additions & 1 deletion javascript/src/URDFClasses.js
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Expand Up @@ -63,6 +63,29 @@ class URDFLink extends URDFBase {
this.isURDFLink = true;
this.type = 'URDFLink';

this.inertial = {
mass: 0,
origin: { xyz: [0, 0, 0], rpy: [0, 0, 0] },
inertia: { ixx: 0, ixy: 0, ixz: 0, iyy: 0, iyz: 0, izz: 0 },
};

}

copy(source, recursive) {

super.copy(source, recursive);

this.inertial = {
mass: source.inertial.mass,
origin: {
xyz: [...source.inertial.origin.xyz],
rpy: [...source.inertial.origin.rpy],
},
inertia: { ...source.inertial.inertia },
};

return this;

}

}
Expand Down Expand Up @@ -122,7 +145,7 @@ class URDFJoint extends URDFBase {
this.jointValue = null;
this.jointType = 'fixed';
this.axis = new Vector3(1, 0, 0);
this.limit = { lower: 0, upper: 0 };
this.limit = { lower: 0, upper: 0, effort: 0, velocity: 0 };
this.ignoreLimits = false;

this.origPosition = null;
Expand All @@ -141,6 +164,8 @@ class URDFJoint extends URDFBase {
this.axis = source.axis.clone();
this.limit.lower = source.limit.lower;
this.limit.upper = source.limit.upper;
this.limit.effort = source.limit.effort;
this.limit.velocity = source.limit.velocity;
this.ignoreLimits = false;

this.jointValue = [...source.jointValue];
Expand Down
33 changes: 33 additions & 0 deletions javascript/src/URDFLoader.js
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Expand Up @@ -364,6 +364,8 @@ class URDFLoader {

obj.limit.lower = parseFloat(n.getAttribute('lower') || obj.limit.lower);
obj.limit.upper = parseFloat(n.getAttribute('upper') || obj.limit.upper);
obj.limit.effort = parseFloat(n.getAttribute('effort') || obj.limit.effort);
obj.limit.velocity = parseFloat(n.getAttribute('velocity') || obj.limit.velocity);

}
});
Expand Down Expand Up @@ -403,6 +405,37 @@ class URDFLoader {
target.urdfName = target.name;
target.urdfNode = link;

// Parse inertial properties
const inertialNode = children.find(n => n.nodeName.toLowerCase() === 'inertial');
if (inertialNode) {

[ ...inertialNode.children ].forEach(n => {

const type = n.nodeName.toLowerCase();
if (type === 'origin') {

target.inertial.origin.xyz = processTuple(n.getAttribute('xyz'));
target.inertial.origin.rpy = processTuple(n.getAttribute('rpy'));

} else if (type === 'mass') {

target.inertial.mass = parseFloat(n.getAttribute('value')) || 0;

} else if (type === 'inertia') {

target.inertial.inertia.ixx = parseFloat(n.getAttribute('ixx')) || 0;
target.inertial.inertia.ixy = parseFloat(n.getAttribute('ixy')) || 0;
target.inertial.inertia.ixz = parseFloat(n.getAttribute('ixz')) || 0;
target.inertial.inertia.iyy = parseFloat(n.getAttribute('iyy')) || 0;
target.inertial.inertia.iyz = parseFloat(n.getAttribute('iyz')) || 0;
target.inertial.inertia.izz = parseFloat(n.getAttribute('izz')) || 0;

}

});

}

if (parseVisual) {

const visualNodes = children.filter(n => n.nodeName.toLowerCase() === 'visual');
Expand Down
75 changes: 75 additions & 0 deletions javascript/test/URDFRobot.test.js
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Expand Up @@ -35,6 +35,81 @@ describe('URDFRobot', () => {
expect(robot.joints.JOINT2.angle).toEqual(2);
});

it('should correctly parse joint efforts and velocities.', () => {
const loader = new URDFLoader();
const robot = loader.parse(`
<robot name="TEST">
<link name="LINK1"/>
<link name="LINK2"/>
<link name="LINK3"/>
<joint name="JOINT1" type="continuous">
<axis xyz="0 0 -1" />
<parent link="LINK1"/>
<child link="LINK2"/>
<limit effort="150" lower="-3.14" upper="3.14" velocity="5.20" />
</joint>
<joint name="JOINT2" type="continuous">
<axis xyz="0 0 -1" />
<parent link="LINK2"/>
<child link="LINK3"/>
</joint>
</robot>
`);

expect(robot.joints.JOINT1.limit.effort).toEqual(150);
expect(robot.joints.JOINT1.limit.lower).toEqual(-3.14);
expect(robot.joints.JOINT1.limit.upper).toEqual(3.14);
expect(robot.joints.JOINT1.limit.velocity).toEqual(5.20);

expect(robot.joints.JOINT2.limit.effort).toEqual(0);
expect(robot.joints.JOINT2.limit.lower).toEqual(0);
expect(robot.joints.JOINT2.limit.upper).toEqual(0);
expect(robot.joints.JOINT2.limit.velocity).toEqual(0);
});

it('should correctly parse joint inertial data.', () => {
const loader = new URDFLoader();
const robot = loader.parse(`
<robot name="TEST">
<link name="LINK1">
<inertial>
<origin rpy="0 0 -1.5707963267948966" xyz="0.14635000035763 0 0"/>
<mass value="2.5076"/>
<inertia ixx="0.00443333156" ixy="0.0" ixz="0.0" iyy="0.00443333156" iyz="0.0" izz="0.0072" />
</inertial>
</link>
<link name="LINK2"/>
<link name="LINK3"/>
<joint name="JOINT1" type="continuous">
<axis xyz="0 0 -1" />
<parent link="LINK1"/>
<child link="LINK2"/>
</joint>
<joint name="JOINT2" type="continuous">
<axis xyz="0 0 -1" />
<parent link="LINK2"/>
<child link="LINK3"/>
</joint>
</robot>
`);

expect(robot.links.LINK1.inertial.origin.rpy).toEqual([0, 0, -1.5707963267948966]);
expect(robot.links.LINK1.inertial.origin.xyz).toEqual([0.14635000035763, 0, 0]);
expect(robot.links.LINK1.inertial.mass).toEqual(2.5076);
expect(robot.links.LINK1.inertial.inertia.ixx).toEqual(0.00443333156);
expect(robot.links.LINK1.inertial.inertia.iyy).toEqual(0.00443333156);
expect(robot.links.LINK1.inertial.inertia.izz).toEqual(0.0072);
expect(robot.links.LINK1.inertial.inertia.ixy).toEqual(0);
expect(robot.links.LINK1.inertial.inertia.ixz).toEqual(0);
expect(robot.links.LINK1.inertial.inertia.iyz).toEqual(0);

// LINK2 has no <inertial> tag — should still have default values
expect(robot.links.LINK2.inertial.mass).toEqual(0);
expect(robot.links.LINK2.inertial.origin.xyz).toEqual([0, 0, 0]);
expect(robot.links.LINK2.inertial.origin.rpy).toEqual([0, 0, 0]);
expect(robot.links.LINK2.inertial.inertia.ixx).toEqual(0);
});

it('should parse material colors and name.', () => {
const loader = new URDFLoader();
const res = loader.parse(`
Expand Down
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